Profile optimization method for helicopter fairing assembly

Abstract

The invention relates to a shape optimization method for helicopter fairing assembly, and belongs to the field of helicopter assembling.The method comprises the steps that deviation distribution of actual manufacturing and theoretical shape of the shape of a helicopter fairing is analyzed; constitutive parameters of fairing composition materials are obtained; establishing a finite element deformation reconstruction model based on a skin theory molded surface; establishing a helicopter fairing assembly finite element model; establishing a helicopter fairing proxy model based on numerical simulation; according to the method, not only can the profile optimization of the weak-rigidity large-span fairing be realized, but also the loading prediction limitation of the fairing under different working conditions can be made up, and theoretical support is provided for the shape optimization design and engineering application of the helicopter fairing.

Description

TECHNICAL FIELD

[0001] The application relates to a fairing shape optimization method, in particular to a fairing shape optimization method for helicopter fairing assembly. BACKGROUND

[0002] During the assembly process of a helicopter fairing, a large assembly deformation is generated, and meanwhile, the fuselage structure is deformed during the change of the fuselage mass and load, so that the assembled power cabin fairing is further deformed. Severe assembly error and deformation can cause the fairing gap, interface error and internal stress to exceed the assembly standard.

[0003] Therefore, it is necessary to control the assembly shape and performance of the weak rigid composite material power cabin fairing, and the fairing shape optimization method for helicopter fairing assembly is proposed by taking the helicopter fairing assembly process as the research object.

[0004] The method can not only greatly reduce the experimental demand and improve the research efficiency, but also can simulate the actual working condition of the fairing of the aircraft under different loads by using the numerical simulation method, and then optimize the shape of the helicopter fairing, so as to make up for the limitation of the experimental means, and thus provide more reliable design basis for engineering application. SUMMARY

[0005] In order to solve the above technical problems, the application provides a fairing shape optimization method for helicopter fairing assembly to solve the problems in the prior art.

[0006] The application aims to provide a fairing shape optimization method for helicopter fairing assembly in the field of helicopter fairing shape optimization methods. The fairing shape optimization method for helicopter fairing assembly aims to combine the numerical simulation method and the multi-objective optimization method, realize the shape optimization of the helicopter fairing in the assembly, improve the process quality control level of the helicopter production line, and provide a new mode of research-production cooperation rapid manufacturing for the development of the helicopter manufacturing line in China.

[0007] The application adopts the following technical scheme:

[0008] A fairing shape optimization method for helicopter fairing assembly, characterized by comprising the following steps:

[0009] S1: scanning and deviation analysis: using a three-dimensional scanner to obtain actual shape point cloud data of the skin in a free state; using PolyWorks software to post-process the point cloud data and analyze the manufacturing deviation distribution thereof relative to a theoretical profile;

[0010] S2: material constitutive parameter acquisition: determining the stress-strain curve of the material of the thin wall of the fairing through a mechanical experiment, and extracting the constitutive parameters of the material according to the stress-strain curve;

[0011] S3: Establishing a finite element deformation reconstruction model based on the skin theory surface: importing the skin theory surface model into the finite element software, assigning the material parameters obtained in S2; based on the point-surface coupling constraint method, applying displacement load to the reference point to construct a deformation reconstruction model based on the skin theory surface controlled by the reference point; through iterative adjustment, ensure that the deviation of the deformation reconstructed by the model is less than 10% of the scanning point cloud result of S1;

[0012] S4: Establishing a finite element simulation of the assembly process of the helicopter fairing: establishing a finite element model of the assembly of the helicopter fairing, importing the skin deformation reconstruction model established in S3; simulating the assembly process based on the deformed theoretical surface, predicting and obtaining the stress and deformation distribution of the fairing in the assembled state;

[0013] S5: Service state simulation and proxy model construction: based on the assembly finite element results of S4, further simulate the deformation of the fairing of the helicopter under the full load condition of installing the main reducer and filling the fuel tank in the finite element software; obtain the internal stress and deformation results under this service state; based on the numerical simulation results, establish a proxy model of the helicopter fairing;

[0014] S6: Fairing shape optimization: based on the non-dominated sorting genetic algorithm (NSGA-II) and the proxy model of the helicopter fairing established in S5, calculate the internal stress and deformation response of different fairing shape schemes under the action of assembly and service load; according to the optimization target (such as minimizing internal stress and deformation), select the optimal fairing shape design scheme.

[0015] Further: the scanning and deviation analysis process specifically includes: placing the fairing skin unconstrainedly on the fixed table, thoroughly cleaning the surface of dust, oil stains and other impurities to ensure that the scanner can accurately capture the surface information; start the scanner and complete the calibration program to make it reach the best working state; evenly paste the positioning target points on the surface of the test piece, plan the scanning station layout; each station needs to ensure that at least 3 common target points are captured, and measurement obstructions are avoided; hold the scanner about 5mm away from the surface of the test piece, move and scan at a stable speed and multiple angles to completely cover all areas of the test piece; transfer the original point cloud data generated by scanning to the computer storage system; import the scanning point cloud data and the theoretical CAD model into the special software PolyWorks, and through registration comparison, quantitatively analyze the actual manufacturing deviation distribution of the skin;

[0016] Further, the material constitutive parameter acquisition specifically comprises: according to the aviation composite material test standard, respectively performing a plane compression test and a three-point bending test on the fairing composite material laminate sample; recording the deformation response of the sample under the action of a gradual load in real time through a high-precision sensor, synchronously generating a load-displacement curve, and outputting an engineering stress-strain curve after coordinate system conversion; based on the least square fitting principle, performing parameter matching on the stress-strain data obtained through the test and a preset constitutive equation, and reversely deducing the elastic modulus, Poisson's ratio and strength parameters representing the mechanical behavior of the laminate;

[0017] Further, the establishment of the finite element deformation reconstruction model based on the skin theory surface specifically comprises: importing the skin theory CAD model of the original design version into the finite element software, creating a static implicit analysis step; assigning the composite material constitutive parameters obtained in claim 2 to the model material properties, and performing adaptive mesh division on the skin by using a second-order reduced integration shell element (S8R); dividing the skin surface into a plurality of material property independent regions according to the actual layup scheme; creating reference points at the centers of the regions, and establishing rigid association between the RP and all nodes in the region through kinematic coupling constraints; applying forced displacement boundary conditions to each reference point to simulate the assembly clamping working condition; submitting the solver for nonlinear static analysis; exporting the deformation results output by the finite element as an STL format, and executing 3D deviation comparison and tolerance verification in the PolyWorks software to ensure that the normal deviation between any point on the surface of the reconstruction model and the scanned point cloud is ≤10%, if the tolerance is exceeded, the material parameters or the constraint conditions are adjusted until the accuracy requirements are met;

[0018] Further, the establishment of the finite element simulation of the assembly process of the helicopter fairing specifically comprises: importing the skin deformation reconstruction finite element model verified in claim 4 and the stiffener theory CAD model into the explicit dynamics solver; based on the constitutive parameters calibrated in claim 3, assigning the corresponding material properties to the skin and the stiffener, the skin uses the S8R shell element, and the stiffener uses the C3D10M solid element, ensuring that the grid size ratio of the contact interface is ≤1:3; according to the relative position relationship defined in the engineering drawing, performing six-degree-of-freedom rigid positioning on the skin reconstruction model and the stiffener model to reproduce the assembly constraint state of the actual tooling fixture; creating an explicit dynamic analysis step, automatically calculating the time step according to the material sound speed stability condition, defining the normal contact as the augmented Lagrangian algorithm and the tangential contact as the Coulomb friction model on the skin-stiffener contact interface, and the contact pair type is a general contact between surfaces; submitting the finite element calculation to obtain the internal stress and deformation of the helicopter fairing after assembly and the deformation finite element model;

[0019] Further, the service state simulation and agent model construction specifically comprises: extracting main load-bearing structures: main reducer support, oil tank support beam, landing gear cabin based on a helicopter CATIA three-dimensional model, establishing a simplified beam-shell hybrid model of the whole machine, simulating the mechanical transmission path of each subsystem through multi-point constraint (MPC); assembling the fairing deformation model output by claim 5 through node mapping technology and the simplified model of the whole machine, setting up freedom coupling constraints at the skin-main reduction support interface; adopting an implicit-explicit sequence solving strategy; based on the established simulation results, constructing a simulation agent model taking the coordinates of the fairing surface control points as input and the equivalent stress / strain as output;

[0020] Further, the shape optimization algorithm based on the agent model specifically comprises: taking the agent model established in step S5 as a response surface engine, selecting skin reference points and skin expansion angles as variable parameters based on the non-dominated sorting genetic algorithm (NSGA-II), taking the stress and deformation of the helicopter fairing assembly as multi-objective optimization parameters, obtaining the internal stress and deformation of the helicopter fairing assembly under different fairing shapes, and selecting the helicopter fairing shape with the minimum internal stress and deformation under the load state. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The present application is a shape optimization method for helicopter fairing assembly.

[0022] Figure 2 The present application is a shape optimization method for helicopter fairing assembly.

[0023] Figure 3 The present application is a shape optimization method for helicopter fairing assembly.

[0024] Figure 4 The present application is a shape optimization method for helicopter fairing assembly.

[0025] Figure 5 The present application is a shape optimization method for helicopter fairing assembly.

[0026] Figure 6 The present application is a shape optimization method for helicopter fairing assembly.

[0027] Figure 7 The present application is a shape optimization method for helicopter fairing assembly.

[0028] Figure 8 The present application is a shape optimization method for helicopter fairing assembly.

[0029] Figure 9The figure shows the process of optimizing the shape of the fairing in the method of the present application. Specific implementation method

[0030] The technical solutions of the present application will be further described in detail below in combination with the drawings and specific implementation modes in the inventive examples.

[0031] As Figure 1 shown.

[0032] A shape optimization method for helicopter fairing assembly, the structure frame is divided into establishing a proxy model of helicopter fairing, and the shape optimization of helicopter fairing based on non-dominated sorting genetic algorithm.

[0033] The present embodiment takes helicopter fairing assembly as an example, the shape of the fairing and its material properties are as Figure 2 shown, and the present description gives the implementation process of the shape optimization method for helicopter fairing assembly:

[0034] Firstly, the actual shape point cloud data of the skin in the free state is obtained by using a three-dimensional scanner; the point cloud data is post-processed by using PolyWorks software to analyze the manufacturing deviation distribution of the theoretical profile, and the specific steps include:

[0035] ①The fairing skin is placed on the fixed table without any constraints, and the surface dust, oil stains and other impurities are thoroughly cleaned to ensure that the scanner can accurately capture the surface information, as Figure 3 shown.

[0036] ②Start the scanner and complete the calibration program to make it reach the best working state; evenly paste the positioning target points on the surface of the test piece; ensure that at least 3 common target points are captured at each station, and avoid measurement obstruction; hold the scanner about 5mm away from the surface of the test piece to move stably at a constant speed and scan at multiple angles to completely cover the entire area of the test piece; transfer the original point cloud data generated by scanning to the computer storage system; import the scanning point cloud data and the theoretical CAD model into the special software, and quantitatively analyze the actual manufacturing deviation distribution of the skin by registration comparison, as Figure 4 shown.

[0037] Secondly, the stress-strain curve of the thin-walled component material of the fairing is determined by the sample stretching test, and the material constitutive parameters are extracted accordingly:

[0038] ①The fairing is a composite material component, and according to the aviation composite material test standard, the composite material laminated plate sample for the fairing is subjected to plane compression test and three-point bending test;

[0039] ②Real-time record the deformation response of the specimen under the action of progressive load by high-precision sensors, and generate the load-displacement curve synchronously. After coordinate system conversion, the engineering stress-strain curve is output, as shown in FIG. 2; Figure 5

[0040] ③Based on the least square fitting principle, the stress-strain data obtained by the test is matched with the preset constitutive equation, and the elastic modulus, Poisson's ratio and strength parameters representing the mechanical behavior of the laminate are reversely deduced

[0041] Step 3: Import the skin theory shape model into the finite element software, and assign it with the material parameters obtained in S2; based on the point-surface coupling constraint method, apply displacement load to the reference point to construct a deformation reconstruction model based on the skin theory surface controlled by the reference point; through iterative adjustment, ensure that the deviation of the deformation reconstructed by the model from the scanning point cloud result of S1 is less than 10%:

[0042] ①Import the original design version of the skin theory CAD model into the finite element software (such as Abaqus / ANSYS), and create a static implicit analysis step;

[0043] ②Assign the model material properties based on the composite material constitutive parameters obtained in claim 2, and use second-order reduced integration shell elements (S8R) for adaptive meshing of the skin;

[0044] ③Divide the skin surface into several material property independent regions according to the actual lay-up scheme;

[0045] ④Create reference points at the centroids of each region, and establish rigid association between the RP and all nodes in the region through kinematic coupling constraints;

[0046] ⑤Apply forced displacement boundary conditions to each reference point to simulate the assembly clamping condition;

[0047] ⑥Submit the solver for nonlinear static analysis; export the deformation results from the finite element output as STL format, and perform 3D deviation comparison and tolerance verification in PolyWorks software to ensure that the normal deviation of any point on the reconstructed model surface from the scanning point cloud is ≤10%, if the tolerance is exceeded, adjust the material parameters or constraint conditions until the accuracy requirements are met, as shown in FIG. 3; Figure 6

[0048] Step 4: Establish the finite element model of the helicopter fairing assembly, and import the skin deformation reconstruction model established in S3 into it; simulate the assembly process based on the deformed theoretical shape, and predict and obtain the stress and deformation distribution of the fairing in the assembled state:

[0049] ①Import the skin deformation reconstruction finite element model verified in claim 4 and the theoretical CAD model of the stiffener into the explicit dynamics solver synchronously; ​​

[0050] ②Based on the constitutive parameters calibrated in claim 3, the corresponding material properties of the skin and the stiffener are assigned respectively. The skin uses S8R shell element, and the stiffener uses C3D10M solid element to ensure that the mesh size ratio of the contact interface is less than or equal to 1:3;

[0051] ③According to the relative position relationship defined in the engineering drawings, the six-degree-of-freedom rigid positioning is performed on the skin reconstruction model and the stiffener model to reproduce the assembly constraint state of the actual tooling fixture;

[0052] ④An explicit dynamic analysis step is created, and the time step is automatically calculated according to the material sound speed stability condition. The normal contact is defined as the augmented Lagrangian algorithm, and the tangential contact is defined as the Coulomb friction model on the skin-stiffener contact interface. The contact pair type is a general contact between surfaces;

[0053] ⑤Submit finite element calculation to obtain the internal stress and deformation of the helicopter fairing after assembly, and the deformation finite element model, as shown in Figure 7 .

[0054] Step 5, based on the assembly finite element results of S4, further simulate the deformation of the helicopter fairing under the full load condition of installing the main reducer and filling the fuel tank in the finite element software; obtain the internal stress and deformation results under this service state; based on the numerical simulation results, establish a surrogate model of the helicopter fairing:

[0055] ①Based on the helicopter CATIA three-dimensional model, extract the main load-bearing structure (including the main reducer support, fuel tank support beam, and landing gear cabin) to establish a simplified beam-shell hybrid model of the whole machine. Simulate the mechanical transmission path of each subsystem through multi-point constraint (MPC), as shown in Figure 8 .

[0056] ②Assemble the fairing assembly deformation model output by claim 5 with the simplified model of the whole machine through node mapping technology, and set the degree of freedom coupling constraint at the skin-main reducer support interface;

[0057] ③Adopt implicit-explicit sequential solving strategy;

[0058] ④Based on the established simulation results, construct a simulation surrogate model with the coordinates of the fairing surface control points as input and the equivalent stress / deformation as output.

[0059] Step 6, based on the non-dominated sorting genetic algorithm (NSGA-II) and the surrogate model of the helicopter fairing established in S5, calculate the internal stress and deformation response of different fairing shape schemes under the action of assembly and service load; according to the optimization objective (such as minimizing internal stress and deformation), select the optimal fairing shape design scheme:

[0060] The agent model established in step S5 is taken as a response surface engine, and based on a non-dominated sorting genetic algorithm (NSGA-II), a skin reference point and a skin expansion angle are selected as variable parameters as shown in Table 1

[0061] Table 1: Selection of optimization parameters of skin reference point and skin expansion angle

[0062]

[0063] With the stress and deformation of the helicopter fairing assembly as multi-objective optimization parameters, the internal stress and deformation of the helicopter fairing under the assembly are obtained under different shapes of the fairing, and the optimized shape of the helicopter fairing with the minimum internal stress and deformation under the loaded state is selected, and the comparison before and after optimization is shown in Table 2, and the optimization process diagram is shown in Figure 9

[0064] Table 3: Comparison before and after optimization of the fairing shape

[0065]

[0066] The principles and implementation modes of the shape optimization method for the helicopter fairing assembly are described, and the above implementation scheme is used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in specific implementation modes and application ranges. In summary, the content of the present application should not be understood as a limitation of the present application.

[0067] The part not involved in the present application is the same as or can be realized by using the prior art.​

Claims

1. A method for optimizing the shape of a helicopter fairing assembly, characterized in that, Includes the following steps: S1: Scanning and Deviation Analysis: Use a 3D scanner to acquire the actual shape point cloud data of the skin in a free state; use PolyWorks software to post-process the point cloud data and analyze its manufacturing deviation distribution from the theoretical surface; S2: Obtaining constitutive parameters of materials: Through mechanical experiments, the stress-strain curves of the thin-walled components of the fairing are measured, and the constitutive parameters of the materials are extracted accordingly. S3: Establish a finite element deformation reconstruction model based on the skin theory surface: Import the skin theory shape model into the finite element software, assign it the material parameters obtained in S2, apply displacement load to the reference point based on the point-surface coupling constraint method, and construct a deformation reconstruction model based on the skin theory surface controlled by the reference point. Through iterative adjustment, ensure that the deviation between the deformation reconstructed by the model and the point cloud result of S1 is less than 10%. S4: Establish a finite element simulation of the helicopter fairing assembly process: Establish a finite element model of the helicopter fairing assembly, import the skin deformation reconstruction model established in S3 into it, simulate the assembly process based on the deformation reconstruction model, and predict and obtain the stress and deformation distribution of the fairing in the assembly state. S5: Service status simulation and proxy model construction: Based on the assembly finite element results of S4, the deformation of the fairing of the helicopter under full load conditions with the main gearbox installed and the fuel tank full is further simulated in the finite element software to obtain the internal stress and deformation results under this service state. Based on this numerical simulation results, a proxy model of the helicopter fairing is established. S6: Fairing Shape Optimization: Based on the non-dominated sorting genetic algorithm (NSGA-II) and the helicopter fairing proxy model established by S5, the internal stress and deformation response of different fairing shape schemes under assembly and service loads are calculated. According to the optimization objective (such as minimizing internal stress and deformation), the optimal fairing shape design scheme is selected.

2. The method for optimizing the shape of a helicopter fairing assembly according to claim 1 is characterized in that, The scanning and deviation analysis process specifically includes: placing the fairing skin flat on a fixed platform without constraints, thoroughly cleaning its surface of dust, oil, and other impurities to ensure the scanner can accurately capture surface information; starting the scanner and completing the calibration procedure to bring it to its optimal working state; evenly pasting positioning target points on the surface of the specimen to plan the layout of the scanning stations; ensuring that each station captures at least 3 common target points and avoiding measurement obstructions; holding the scanner about 5mm away from the surface of the specimen and moving it at a stable and uniform speed at multiple angles to completely cover the entire area of ​​the specimen; transferring the raw point cloud data generated by the scan to the computer storage system; importing the scanned point cloud data and the theoretical CAD model into the dedicated software PolyWorks, and quantitatively analyzing the distribution of actual manufacturing deviations of the skin through registration and comparison.

3. The method for optimizing the shape of a helicopter fairing assembly according to claim 1 is characterized in that, The acquisition of material constitutive parameters specifically includes: conducting planar compression tests and three-point bending tests on composite laminate specimens for fairings according to aerospace composite material testing standards; recording the deformation response of specimens under progressive loading in real time using high-precision sensors, simultaneously generating load-displacement curves, and outputting engineering stress-strain curves after coordinate system transformation; and based on the least squares fitting principle, matching the stress-strain data obtained from the tests with the preset constitutive equations to derive the elastic modulus, Poisson's ratio, and strength parameters characterizing the mechanical behavior of the laminate.

4. The method for optimizing the shape of a helicopter fairing assembly according to claim 1 is characterized in that, The establishment of a finite element deformation reconstruction model based on the skin theory surface specifically includes: importing the original design version of the skin theory CAD model into the finite element software and creating a static implicit analysis step; assigning material properties to the model based on the composite material constitutive parameters obtained in claim 2, and using second-order reducing shell elements (S8R) to adaptively mesh the skin; dividing the skin surface into several material property-independent regions according to the actual layup scheme; creating reference points at the centroid of each region, and establishing a rigid connection between the RP and all nodes in the region through kinematic coupling constraints; applying forced displacement boundary conditions to each reference point to simulate assembly clamping conditions; Submit the solver for nonlinear static analysis; export the deformation results from the finite element analysis to STL format, and perform 3D deviation comparison and tolerance verification in PolyWorks software to ensure that the normal deviation between any point on the surface of the reconstructed model and the scanned point cloud is ≤10%. If the deviation exceeds the tolerance, adjust the material parameters or constraints until the accuracy requirements are met.

5. The method for optimizing the shape of a helicopter fairing assembly according to claim 1 is characterized in that, The establishment of a finite element simulation of the helicopter fairing assembly process specifically includes: synchronously importing the skin deformation reconstruction finite element model verified by claim 4 and the stiffener theoretical CAD model into an explicit dynamic solver; based on the constitutive parameters calibrated in claim 3, assigning corresponding material properties to the skin and stiffener respectively, with the skin using S8R shell elements and the stiffener using C3D10M solid elements, ensuring that the mesh size ratio at the contact interface is ≤1:3; performing six-degree-of-freedom rigid positioning on the skin reconstruction model and stiffener model according to the relative positional relationship defined in the engineering drawings to reproduce the assembly constraint state of the actual tooling fixture; creating an explicit dynamic analysis step, with the time step automatically calculated according to the material sound velocity stability condition, defining the normal contact at the skin-stiffener contact interface as the augmented Lagrangian algorithm, the tangential contact as the Coulomb friction model, and the contact pair type as surface-to-surface universal contact; Submit finite element calculations to obtain the internal stress and deformation of the helicopter fairing after assembly, as well as the deformation finite element model.

6. The method for optimizing the shape of a helicopter fairing assembly according to claim 1 is characterized in that, The service status simulation and proxy model construction specifically includes: based on the helicopter CATIA 3D model, extracting the main load-bearing structures: main gearbox bracket, fuel tank support beam, and landing gear bay, establishing a simplified beam-shell hybrid model of the whole aircraft, and simulating the mechanical transmission path of each subsystem through multi-point constraint (MPC); assembling the fairing assembly deformation model output by claim 5 with the simplified model of the whole aircraft through node mapping technology, and setting degree-of-freedom coupling constraints at the skin-main gearbox bracket interface; adopting an implicit-explicit sequential solution strategy; and based on the established simulation results, constructing a simulation proxy model with the coordinates of the fairing surface control points as input and the equivalent stress / deformation as output.

7. The method for optimizing the shape of a helicopter fairing assembly according to claim 1 is characterized in that, The surrogate model-based shape optimization algorithm specifically includes: using the surrogate model established in step S5 as the response surface engine, based on the non-dominated sorting genetic algorithm (NSGA-II), selecting the skin reference point and skin expansion angle as variable parameters, and using the helicopter fairing assembly stress and deformation as multi-objective optimization parameters, obtaining the internal stress and deformation of the helicopter fairing under different shape conditions, and selecting the helicopter fairing with the minimum internal stress and deformation under load to optimize the shape.

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